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Structure of a web application

Structure of a web application. Dr Jim Briggs. MVC. MVC. Model View Controller pattern Way of keeping aspects of an application separate Applicable to all applications, not just web ones. Advantages of MVC. Good software engineering practice to maintain separation of concerns

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Structure of a web application

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  1. Structure of a web application Dr Jim Briggs Structure of a web application

  2. MVC Structure of a web application

  3. MVC • Model View Controller pattern • Way of keeping aspects of an application separate • Applicable to all applications, not just web ones Structure of a web application

  4. Advantages of MVC • Good software engineering practice to maintain separation of concerns • An application might have more than one user interface • The elements of the user interface need to be kept separate from the parts that are common to each • Different developers (with different skills) may be responsible for different aspects of the application • Frequently, user-interface designers responsible for the view • Conventional programmers responsible for the controller and model • In some circumstances, the controller might be the responsibility of an interaction engineer (or team) Structure of a web application

  5. The structure of MVC Structure of a web application

  6. Implementing webapps in Java • Type 1 – all in JSP • Type 1.5 – JSPs that call JavaBeans to do most of the processing • Type 2 – very little code in JSPs; servlet used as controller; JavaBeans provide model Structure of a web application

  7. Type 1.5 Structure of a web application

  8. Type 2 Structure of a web application

  9. Application layers Structure of a web application

  10. 3-tier Application Architecture 3-tier architecture External Presentation User Other Apps Business Logic Database Data Access Structure of a web application

  11. This is what the user sees and interacts with Sometimes called the GUI or client view Should not contain business logic or data access code Presentation Layer 3-tier architecture Presentation Business Logic Data Access Structure of a web application

  12. The set of rules for processing business information Sometimes called middle tier or backend Should not contain presentation or data access code Logic (Business) Layer 3-tier architecture Presentation Business Logic Data Access Structure of a web application

  13. The physical storage layer for data persistence Manages access to DB or file system Should not contain presentation or business logic code Data Access Layer 3-tier architecture Presentation Business Logic Data Access Structure of a web application

  14. Each tier should be independent and should not expose dependencies related to the implementation Unconnected tiers should not communicate The 3-tier principles 3-tier architecture Presentation Business Logic Data Access Structure of a web application

  15. How tiers affect design Structure of a web application

  16. Implementation architectures Structure of a web application

  17. Single server (abstract) Structure of a web application

  18. Single server (servlet/JSP) Structure of a web application

  19. Single server (JSF) Structure of a web application

  20. Separate servers (abstract) Structure of a web application

  21. Separate servers (servlets/JSP) Structure of a web application

  22. Separate servers (JSF) Structure of a web application

  23. Java Beans Structure of a web application

  24. JavaBeans • A JavaBean is a Java class that: • has a parameterless constructor • (it could have other constructors as well) • is capable of holding state through one or more private instance variables • (and if necessary saving it to a persistent store) • implements a method called getX that returns the value of readable property X • implements a method called setX that changes the value of writable property X • (has both a setter and a getter for a read/write property) • may also fire, and respond to, events • (but that ability is not important for our purposes at the moment) Structure of a web application

  25. Enterprise JavaBeans • Entity beans • Session beans • Stateless • Stateful • Singleton • Message beans • Dependency injection • State management • Transaction management • Security • Pooling • Interceptors Structure of a web application

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